An example of a universal joint of the above-described type, sometimes called a Cardan joint, is described in DE 103 02 069 A1 (a family member of U.S. Pat. No. 7,258,490). In such universal joints, disc springs are typically used in the trunnion bearings to apply an axial force on the rolling elements. The use of disc springs ensures that if the rolling elements are joggled or displaced while under load, they will be brought back into their proper coaxial orientation when the load is removed (when the bearing returns to an unloaded state). The universal joint can thereby be protected from excessive wear, friction, and material stress.
Furthermore, universal joints of the above-described type are generally provided with seals to protect the trunnion bearing, which bearing is usually embodied as a needle bearing. These seals must function in the presence of highly abrasive contaminants. For example, bearings used in motor vehicles, especially those that operate in dusty environments like construction zones, may be exposed to contaminants that can contaminate the universal joints.
To date inner and outer seals (two separate seal systems) have been used in universal joints. By way of example, reference is made to the above-mentioned DE 103 02 069 A1, that shows separate inner and outer seals.
The use of the disc springs in conventional universal joint bushings increases manufacturing expense and installation effort.
Furthermore, it has been found that elastomeric seal lips sometimes do not provide an optimal sealing against water, sand, and mud. Instead, adequate sealing can only be achieved by using an inner seal and an outer seal. This can easily lead to wear on the outer seal lip.
A disadvantage of conventional trunnion bearings, including those in the cited document, is that they require a construction of a relatively expensive inner seal in order to ensure that penetrating dirt is kept away from the region of the trunnion bearing. Conventional assemblies that use two separate seal systems and disc springs are thus expensive and correspondingly expensive to manufacture and install.